<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>bootstrap</title>
    <style>
        h1{
            font-size: 14px;
        }
        @media screen and (min-width: 768px){
            h1 {
                font-size: 80px;
            }
        }
    </style>
</head>
<body>
    <h1>响应式布局</h1>
</body>
</html>